METHOD AND SYSTEM FOR OPERATING AND MONITORING A WELL FOR EXTRACTING OR STORING FLUID

Abstract

The system for operating and monitoring a well for extracting or storing an operating fluid, such as natural gas, comprises a production column in which the operating fluid flows, a protective casing arranged around the production column, and a cement sheath interposed between the casing and a rock formation through which the well extends. The system further comprises, outside the casing, between the casing and the cement sheath, a series of electronic units distributed in predetermined positions in a succession of planes perpendicular to the casing and spaced apart axially along the casing. Each electronic unit comprises communication means enabling the electronic unit to communicate with another electronic unit or with a surface terminal, a power supply unit of the electronic unit, and at least one of the following elements: a) a detector unit comprising at least one sensor for sensing a physical or chemical magnitude, and b) a signal processor unit.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §365 to International Patent Application No. PCT/FR2015/051469 filed on Jun. 3, 2015, which claims priority to French Patent Application No. 1455078 filed on Jun. 4, 2014. Both of these applications are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a system for operating and monitoring a well for extracting or storing an operating fluid such as natural gas, the well comprising a production column in which the operating fluid flows, protective casing arranged around the production column, and a cement sheath interposed between the casing and a rock formation through the well extends.

The invention also provides a method of operating and monitoring a well for extracting or storing an operating fluid, the monitoring including tracking the placing and the integrity of the cement protection barrier.

The integrity of a well for extracting or storing a fluid such as a hydrocarbon or natural gas can be affected by the presence of voids while cement is being used to fill the annular gap situated between the casing of the extraction well and the surrounding rock, or indeed as a result of the cement aging. These two factors can give rise to unwanted stoppages of production, which, by their very nature, are not foreseeable, unless the integrity of the cement sheath is monitored regularly.

It is therefore desirable to be able to inspect the integrity of the cement sheath in reliable and effective manner in order to be able to predict stoppages of production and act appropriately to minimize the losses of production associated with stopping operation.

There exist probes and well-logging methods that enable a well to be inspected at a point in time. The state (cracks or voids) of the cement can thus be observed and poor quality cementing can be identified (i.e. places where the annular space is incompletely filled). A major drawback of that method is that it is intrusive and requires production to be stopped, since the probe needs to be inserted inside the casing, which involves removing the production column.

Indirect measurements are also known for detecting leaks, such as analyzing fluids or analyzing pressure outside the well, for example. Nevertheless, such indirect methods serve to confirm a problem but not to anticipate it.

Thus, logging and indirect measurements do not enable cement to be tracked over the long term, nor do they enable cementing to be inspected so as to provide a method that is suitable for anticipating production stoppages.

Proposals have already been made to disperse sensors in the cement sheath interposed between the casing and the well for extracting or storing fluid and the rock formation through which the well extends, for the purposes of inspecting the integrity of the cement sheath and of monitoring its aging. Nevertheless, acting in that way does not make it possible to guarantee that sensors are distributed in uniform manner within the cement sheath. Furthermore, the nanometric size of embedded sensors, as is required for incorporating the sensors in cement, prevents independent and non-wired sensors being electrically powered and being able to communicate among one another, as is necessary for them to operate.

Also known, from Document WO 2011/017415 A2 is a borehole fitted with temperature sensors and strain gauges distributed along the casing between the casing and the cement sheath, which sensors may be placed in successive horizontal planes or else arranged following a helical path.

SUMMARY

The present invention seeks to remedy the above-mentioned drawbacks and to make it possible to inspect in reliable and effective manner the proper placing and integrity of the cement sheath situated between a casing and a rock formation, in order to be able to predict stoppages of production in the well for extracting or storing fluid and to act accordingly in order to minimize production losses associated with stopping operation.

These objects are achieved in accordance with the invention by means of a system for operating and monitoring an extraction or storage well for an operating fluid such as a hydrocarbon, geothermal water, carbon dioxide, or natural gas, the well comprising a production column in which said operating fluid flows, a protective casing arranged around the production column via an annulus fluid, and a cement sheath interposed between the casing and a rock formation through which the well extends, the system being characterized in that it comprises, outside the casing, between the casing and the cement sheath, a series of electronic units distributed in predetermined positions in a succession of planes perpendicular to the casing and spaced apart axially along the casing, each electronic unit comprising communication means enabling the electronic unit to communicate with another electronic unit or with a surface terminal, a power supply unit of the electronic unit, and at least one of the following elements: a) a detector unit comprising at least one sensor for sensing a physical or chemical magnitude, and b) a signal processor unit, and in that at least one electronic unit is arranged as a relay unit in which the communication means include means for receiving signals transmitted by surrounding electronic units and means for transmitting signals received from the surrounding electronic units and amplified by a signal processor unit.

Each detector unit may comprise a sensor corresponding to measuring a single type of physical or chemical magnitude.

Nevertheless, in a variant embodiment, each detector unit comprises a set of a plurality of sensors corresponding to measuring a plurality of different physical or chemical magnitudes.

The independent sensors making it possible to measure a physical or chemical magnitude in the volume of the cement sheath in order to inspect its integrity may in particular comprise ultrasound sensors, radar sensors, and/or terahertz sensors, and additionally temperature sensors and/or strain gauges.

Depending on the intended application, between one to eight electronic units are distributed around the casing in a common plane perpendicular to said casing.

In a preferred particular embodiment, the communication means comprises wireless communication means, such as radiowaves, electromagnetic waves, soundwaves, or surface currents.

Radio communication means for returning information by radio frequency in the cement sheath preferably make use of a frequency lying in the range 169 megahertz (MHz) to 2.4 gigahertz (GHz). This makes it possible to combine an antenna of reasonable size (of centimeter order) with range that is sufficient (of the order of about ten meters).

In another possible embodiment, the communication means comprise wired communication means.

The electronic units may be fastened directly on the casing by a mechanical connection, such as adhesive, soldering, or welding.

In a particular embodiment, the electronic units are put directly into contact with the casing, the electronic units and the casing then being covered by a protective polymer layer for protecting the electronic units and the casing and for ensuring that the electronic units are held on the casing.

In another embodiment, the electronic units are arranged on a continuous strip that is adhesively bonded on a generator line of the casing and that is in contact with the cement sheath.

The invention makes it possible to arrange sensors at very precise locations along the casing.

In an embodiment, a first series of electronic units of a first type are arranged in planes perpendicular to the casing that are spaced apart axially at a large first mesh, and a second series of electronic units of a second are arranged in planes perpendicular to the casing that are spaced apart axially in a smaller second mesh.

By way of example, the electronic units including at least one detector unit are arranged in planes perpendicular to the casing that are spaced apart axially from one another by 10 centimeters (cm) to 10 meters (m).

The electronic units not including a detector unit may be arranged in planes perpendicular to the casing that are spaced apart axially from one another by 5 m to 100 m.

In particular, the invention provides a system in which the detector units include at least one sensor selected from sensors of temperature, pressure, strain, or integrity, such as a sensor for sensing density, the presence of material, or the chemical environment, such as the presence of water or sulfur.

In a particular embodiment, the electronic units have thickness lying in the range 1 millimeters (mm) to 20 mm.

The power supply unit of each electronic unit comprises electrical energy storage means, such as a battery or a supercapacitor.

In particular, it is possible to use high temperature batteries, such as solid cathode lithium batteries having a capacity of about 10 watt hours (Wh) to 50 Wh as a function of the data transmission protocol used, or indeed a system of micro fuel cells.

The power supply unit of each electronic unit may equally well comprise means for receiving energy, such as electromagnetic energy transmitted along the casing or mechanical or thermal energy collected by means of magneto-inductive, piezoelectric, or Seebeck transducers.

Thus, in a particular embodiment, at least one electronic unit arranged as a relay unit recovers energy from the surrounding medium in order to power the at least one detector unit comprising at least one sensor for sensing a physical or chemical magnitude and/or the at least one signal processor unit. Energy may also be obtained in particular by collecting thermal energy from the well by using the temperature gradient between the surrounding medium and the operating fluid.

The invention also provides a fabrication method for fabricating the casing of a well for extracting or storing an operating fluid, the method being characterized in that it comprises the steps consisting in:

providing a set of casing elements;

prior to inserting each casing element in the extraction well, fastening thereon a series of electronic units distributed in predetermined positions in a succession of planes perpendicular to the casing and spaced apart axially along the casing, each electronic unit comprising communication means enabling the electronic unit to communicate with another electronic unit or with a surface terminal, a power supply unit of the electronic unit, and at least one of the following elements: a) a detector unit comprising at least one sensor for sensing a physical or chemical magnitude, and b) a signal processor unit, at least one electronic unit being arranged as a relay unit in which the communication means include means for receiving signals transmitted by surrounding electronic units and means for transmitting signals received from the surrounding electronic units and transformed by a signal processor unit; and

fastening the casing elements together end-to-end to form the casing.

In this method of fabricating the casing of an extraction well, the step of fastening electronic units on the casing is performed on a generator line of the casing element by adhesive, soldering, or welding, and the electronic units are covered by a protective polymer layer.

The invention also provides a method of operating and monitoring a well for extracting or storing an operating fluid such as a hydrocarbon, geothermal water, carbon dioxide, or natural gas, the method comprising the steps consisting in making a borehole in a geological formation, arranging a protective casing in the borehole, and interposing a sheath of cement between the casing and the geological formation, the method being characterized in that the casing is made in accordance with the above-defined fabrication method.

BRIEF DESCRIPTION OF THE DRAWING

Other characteristics and advantages of the invention appear from the following description of particular embodiments given as examples, with reference to the accompanying drawing, in which:

FIG. 1 is a diagrammatic vertical section view of a well fitted with an operating and monitoring system of the invention;

FIG. 2 is a section view on line II-II of FIG. 1; and

FIG. 3 is a block diagram showing the essential components of an example of an electronic unit suitable for being used in the operating and monitoring system of the invention.

DETAILED DESCRIPTION

FIG. 1 shows an example of a well for extracting or storing an operating fluid such as a hydrocarbon, geothermal water, carbon dioxide, or natural gas, to which the invention is applicable. FIG. 1 shows a vertical well, but the invention is equally applicable to a well that is inclined relative to the vertical.

FIG. 1 shows a production column 20 in which the operating fluid flows, a protective casing 60 arranged around the production column 20 via an annulus fluid 25, and a cement sheath interposed between the casing 60 and a rock formation 70 through which the well extends. Outside the casing 60, between the casing the cement sheath 30, a series of electronic units 110 are distributed in predetermined positions in a succession of planes perpendicular to the casing 60 and spaced apart axially along the casing 60.

As shown diagrammatically in FIG. 3, each electronic unit 110 comprises at least communication means 14 enabling the electronic unit 110 to communicate with another electronic unit or with a surface terminal 100, and a power supply unit 13 of the electronic unit together with at least one of the following elements:

a) a detector unit comprising at least one sensor 11 for sensing a physical or chemical magnitude; and

b) a signal processor unit 12.

An electronic unit 110 having only a detector unit of point a) is thus an independent unit arranged to take measurements of at least one physical or chemical magnitude and to transmit the taken measurements either to another electronic unit 110 acting as a relay for the measurements, or else to a surface terminal 100 that serves to collect and analyze the measurement data that has been measured.

An electronic unit having only a processor unit 12 of point b) is thus a relay arranged to receive data from other electronic units 110, in particular sensors of a physical or chemical magnitude, and to forward the data either to another electronic unit 110 that also acts as a relay, or else to the surface terminal 100. The signal processor unit 12 serves to filter and transform signals it receives in order to preserve the quality of the forwarded signal. Such an electronic unit 110 also includes signal receiver means, such as an antenna suitable for the signal. For greater clarity, the electronic unit 110 suitable for relaying signals is referred to below as a relay unit.

The electronic units 110 may be arranged to comprise both a detector unit with a sensor 11 and a signal processor unit 12 in order to combine the functions of being a relay and of measuring physical or chemical magnitudes, as shown in FIG. 3.

Each detector unit may have either a sensor 11 corresponding to a single type of physical or chemical magnitude, or else a set comprising a plurality of sensors 11 for sensing different physical or chemical magnitudes.

FIG. 2 shows an assembly comprising a single electronic unit 110 situated in a given horizontal plane perpendicular to the vertical casing 60, but this number could be different. Thus, in general manner, between one to eight electronic units 110 may be arranged around the casing 60 in a single plane perpendicular to the casing 60.

The communication means 14 associated with the electronic units 110 may comprise wireless communication means, e.g. using radiowaves, soundwaves, electromagnetic waves, or surface currents, or in another embodiment, they may comprise wired communication means.

Radio communication means for returning information by radio in the cement sheath preferably use a frequency lying in the range 169 MHz to 2.4 GHz. This makes it possible to combine an antenna of size that is reasonable (of centimeter order) and a range that is sufficient (of the order of about ten meters).

The electronic units 110 may be fastened directly to the casing 60 or they may be arranged on a continuous strip 61 that is adhesively bonded to a generator line of the casing 60 and that is in contact with the cement sheath 30. In a particular embodiment, the sensors are fastened to a metal belt that is then closed and tightened around the casing 60.

The electronic units 110 may include transmission means 12 adapted to transmit the measurement signals from one to the next towards a base 100 situated at the surface of the ground.

The electronic units 110 may be fastened to the casing 60 by adhesive or they may be fastened to a flexible support surrounding the casing 60.

When the casing 60 is made of steel, the electronic units 110 may also be fastened to the casing 60 by welding or soldering.

In a preferred embodiment, the electronic units 110 are put directly into contact with the casing 60, the electronic units 110 and the casing 60 then being covered by a protective polymer layer 61 for protecting the electronic units and the casing while bending and conditioning the casing and during manipulations before and during laying of the casing, and also for holding the electronic units 110 on the casing 60.

The electronic units 110 typically include microcomponents in order to reduce the size of each electronic unit. Thus, the electronic units 110 typically present thickness lying in the range 1 mm to 20 mm. The electronic units 110 can thus be covered in a protective polymer layer 61.

Nevertheless, incorporating certain components, such as a battery for example, can lead to the electronic units 110 being thicker, e.g. having thickness up to as much as 50 mm. Under such circumstances, the casing 60 should include housings of size and depth corresponding to the electronic units 110 so that they are embedded in the casing prior to applying the protective polymer layer 61.

In a configuration that is advantageous, but not exclusive, a first series of electronic units 110, each having a detector element 11 for detecting a first type of physical or chemical magnitude, are arranged in planes perpendicular to the casing 60 that are spaced apart axially at a large first mesh of length L1 and in FIG. 1 they are referenced as being the units 111, 112, 115, 116, and 118.

Under such circumstances, a second series of electronic units 110, each including a detector element 11 for detecting a second type of physical or chemical magnitude, are arranged in planes perpendicular to the casing 60 that are spaced apart axially at a smaller second mesh of length L2 over at least a fraction of the height of the casing 60, and they are referenced in FIG. 1 as being the units 113 and 114 situated level with the formation 40, and the units 116 and 117 situated level with the formation 50. It should be observed that units such as the unit 116 may be common to both meshes in which case they have detector elements 11 for detecting both the first and the second types of physical or chemical magnitude.

The electronic units 110 may be arranged in planes perpendicular to the casing 60 that are spaced apart axially from one another, e.g. in the range 10 cm to 100 m, however other ranges of values are possible depending on the applications.

Advantageously, the electronic units 110 having at least one detector unit are arranged in planes perpendicular to the casing 60 that are spaced apart axially from one another in the range 10 cm to 10 m in order to create a sensor mesh suitable for detecting modifications in the cement sheath 30. In addition, the mesh of sensors 11 may be modulated depending on the geological layers encountered. Thus, the mesh of temperature or pressure sensors may be adapted to the depth of the borehole, with the mesh becoming denser with increasing depth of the borehole.

In similar manner, electronic units 110 that do not have at least one detector unit, in particular the relay units, are arranged in planes perpendicular to the casing 60 that are spaced apart axially from one another by a distance in the range 5 m to 100 m, i.e. at a larger mesh, but suitable for enabling the electronic units 110 to communicate with one another.

More generally, in a preferred embodiment of the invention, each sensor 11 has its own mesh, the relay units being arranged so that each sensor 11 can send data to the surface terminal 100. Whenever possible, the sensors and/or relays are grouped together in an electronic unit 110 in order to facilitate implementation.

The detector units comprise at least one sensor 11 selected from sensors for sensing the following physical magnitudes: temperature, pressure, strain, and integrity, such as the density or the presence of material in order to detect missing cement, chemical environment, such as the presence of water or sulfur, in order to detect infiltration of water or of elements that might affect the casing 60.

By way of example, the electronic units 113, 114 and 116, 117 may comprise a first series of detector units, each comprising a pressure sensor, and the electronic units 111, 112, 115, 116, and 118 may comprise a second series of detector units each comprising a temperature sensor.

Under such circumstances, the electronic units 113, 114 and 116, 117 of the first series may be arranged in planes perpendicular to the casing 60 that are spaced apart axially from one another by a length L2 lying in the range 50 cm to 150 cm, and the electronic units 111, 112, 115, 116, and 118 of the second series may be arranged in planes perpendicular to the casing 60 that are spaced apart axially from one another by a length L1 lying in the range 5 m to 15 m.

According to a particular characteristic, the detector units of the electronic units 110 are electrically powered by means for receiving energy, such as electromagnetic energy transmitted along the casing 60. Electrical power supply may also be obtained by collecting mechanical and thermal energy, e.g. by means of magneto-inductive, piezoelectric, or Seebeck effect transducers.

Thus, in a particular embodiment, at least one electronic unit arranged as a relay unit recovers energy from the surrounding medium in order to power at least one detector unit having at least one sensor for sensing a physical or chemical magnitude and/or at least one signal processor unit. Energy may also be obtained in particular by collecting thermal energy from the well and using the temperature gradient between the surrounding medium and the operating fluid.

In another embodiment, each electronic unit 110 has an independent battery or electrical power supply capacitors constituting the energy source 13.

The invention also provides a method of fabricating the casing 60 of a well for extracting or storing an operating fluid, the method consisting in:

providing a set of casing elements;

prior to inserting each casing element in the extraction well, fastening thereon each casing element a series of electronic units 110 distributed in predetermined positions in a succession of planes perpendicular to the casing 60 and spaced apart axially along the casing 60, each electronic unit 110 comprising communication means 14 enabling the electronic unit 110 to communicate with another electronic unit 110 or with a surface terminal 100, a power supply unit 13 of the electronic unit 110, and at least one of the following elements: a) a detector unit comprising at least one sensor 11 for sensing a physical or chemical magnitude, and b) a signal processor unit 12; and

fastening the casing elements together end-to-end in order to form the casing.

The casing elements are tubes, generally made of steel and having a length of 10 m, for example, and they are produced in a factory, with the complete casing thus being obtained by way of example by screwing these various elements together end to end. In the invention, these casing elements are fitted with electronic units 110 as defined above in the factory. The casing elements are then assembled while making the extraction well.

More precisely, in a preferred embodiment of the invention, the electronic units 110 are arranged on the casing 60 by temporary adhesive. Then the casing 60 and the electronic units 110 are covered by a protective polymer layer 61, which fastens the electronic units 110 on the casing 60. This layer 61 is selected so as to enable the sensors 11 to be used while enabling the electronic units 110 to be fastened to the casing 60.

The method also includes steps consisting in installing, outside the casing 60, between the casing and the cement sheath 30, a series of electronic units 110, comprising detector units and/or relay units, that are distributed in predetermined positions in a succession of planes perpendicular to the casing 60 and spaced apart axially along the casing 60. Each detector unit comprises at least one sensor 11 for sensing a physical or chemical magnitude, communication means 14 for signals coming from the sensor 11, a power supply unit 13, and where appropriate a signal processor unit 12 for processing signals from the sensor 11. Each relay unit comprises signal transmission means 14, a power supply unit 13, and where appropriate a unit 12 for processing the relayed signals. FIG. 3 shows an electronic unit 110 combining both the functions of a detector unit and the functions of a relay unit.

Claims

1. A system for operating and monitoring an extraction or storage well for an operating fluid, the well comprising (i) a production column in which the operating fluid flows, (ii) a protective casing arranged around the production column, and (iii) a cement sheath interposed between the casing and a rock formation through which the well extends, the system comprising:

outside the casing, between the casing and the cement sheath, a series of electronic units distributed in specified positions in a succession of planes perpendicular to the casing and spaced apart axially along the casing, each electronic unit comprising (i) a communication unit configured to enable the electronic unit to communicate with another electronic unit or with a surface terminal, (ii) a power supply, and (iii) at least one of: (a) a detector comprising at least one sensor configured to sense a physical or chemical magnitude or (b) a signal processor;

wherein at least one of the electronic units is configured as a relay in which the communication unit comprises a receiver configured to receive signals transmitted by one or more surrounding electronic units and a transmitter configured to transmit signals received from the one or more surrounding electronic units and transformed by the signal processor.

2. The system according to claim 1, wherein each detector comprises a sensor configured to measure a single type of physical or chemical magnitude.

3. The system according to claim 1, wherein each detector comprises a plurality of sensors configured to measure a plurality of different physical or chemical magnitudes.

4. The system according to claim 1, wherein one to eight electronic units are distributed around the casing in a common plane perpendicular to the casing.

5. The system according to claim 1, wherein the communication unit comprises a wireless radio.

6. The system according to claim 1, wherein the communication unit comprises a wired communication unit.

7. The system according to claim 1, wherein the electronic units are fastened directly on the casing.

8. The system according to claim 1, further comprising:

a protective polymer layer configured to protect the electronic units and the casing and configured to hold the electronic units on the casing.

9. The system according to claim 1, wherein the electronic units are arranged on a continuous strip that is adhesively bonded on a generator line of the casing and that is in contact with the cement sheath.

10. The system according to claim 1, wherein:

a first series of electronic units of a first type is arranged in planes perpendicular to the casing that are spaced apart axially at a larger first mesh; and

a second series of electronic units of a second type is arranged in planes perpendicular to the casing that are spaced apart axially at a smaller second mesh.

11. The system according to claim 1, wherein the electronic units including the detectors are arranged in planes perpendicular to the casing that are spaced apart axially from one another by 10 cm to 10 m.

12. The system according to claim 1, wherein the electronic units not including the detectors are arranged in planes perpendicular to the casing that are spaced apart axially from one another by 5 m to 100 m.

13. The system according to claim 1, wherein the detectors are configured to detect at least one of: temperature, pressure, strain, integrity, density, a presence of material, or a chemical environment.

14. The system according to claim 1, wherein the electronic units have a thickness of 1 mm to 20 mm.

15. The system according to claim 1, wherein the power supply of each electronic unit comprises a battery or a supercapacitor.

16. The system according to claim 1, wherein the power supply of each electronic unit is configured to receive electromagnetic energy transmitted along the casing or mechanical or thermal energy collected by magneto-inductive, piezoelectric, or Seebeck transducers.

17. The system according to claim 1, wherein the at least one electronic unit configured as the relay is configured to recover energy from a surrounding medium in order to power at least one of: the detector or the signal processor.

18. A method for fabricating a casing of a well for extracting or storing an operating fluid, the method comprising:

providing a set of casing elements;

prior to inserting the casing elements in the well, fastening thereon a series of electronic units to be distributed in specified positions in a succession of planes perpendicular to the casing and spaced apart axially along the casing, each electronic unit comprising (i) a communication unit configured to enable the electronic unit to communicate with another electronic unit or with a surface terminal, (ii) a power supply, and (iii) at least one of: (a) a detector comprising at least one sensor configured to sense a physical or chemical magnitude or (b) a signal processor, at least one of the electronic units configured as a relay in which the communication unit comprises a receiver configured to receive signals transmitted by one or more surrounding electronic units and a transmitter configured to transmit signals received from the one or more surrounding electronic units and transformed by the signal processor; and

fastening the casing elements together end-to-end to form the casing.

19. The method according to claim 18, wherein the electronic units are fastened on a generator line of the casing elements by adhesive, soldering, or welding.

20. The method according to claim 18, wherein the electronic units are covered by a protective polymer layer.

21. A method of operating and monitoring a well for extracting or storing an operating fluid, the method comprising:

making a borehole in a geological formation;

arranging a protective casing in the borehole; and

interposing a sheath of cement between the casing and the geological formation;

wherein the casing is made by: obtaining a set of casing elements; prior to inserting the casing elements in the well, fastening thereon a series of electronic units to be distributed in specified positions in a succession of planes perpendicular to the casing and spaced apart axially along the casing, each electronic unit comprising (i) a communication unit configured to enable the electronic unit to communicate with another electronic unit or with a surface terminal, (ii) a power supply, and (iii) at least one of: (a) a detector comprising at least one sensor configured to sense a physical or chemical magnitude or (b) a signal processor, at least one of the electronic units configured as a relay in which the communication unit comprises a receiver configured to receive signals transmitted by one or more surrounding electronic units and a transmitter configured to transmit signals received from the one or more surrounding electronic units and transformed by the signal processor; and fastening the casing elements together end-to-end to form the casing.